A report by the International Energy Agency found that 6.5 million deaths per year can be attributed to air pollution. As the air quality in many cities declines, the risk of stroke, heart disease, lung cancer, and chronic and acute respiratory diseases, including asthma, increases for the people who live in them. The air quality is the worst in India, China and the Middle East. The major sources of pollution come from the exhaust fumes from vehicles, manufacturing facilities and power plants. The following are the 30 most polluted cities in the world.